Automatic interlocking apparatus



Nov. 23 ,1926. 1,608,044

L. E. SPRAY AUTOMATIC INTERLOCKING APPARATUS Filed Feb. 21, 1924INVENTOR; I Q; 1.?

Patented New 23, 1926 siren STATES PATENT 1 orricn LESTER E. SPRAY, O1VJILZIINSBUR G, PENNSYLVANIA, ASSIGNOB' TO UNION SWITCH & SIGNALCOMPANY, OF SVISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

AUTOMATIC INTERLOQKING APPARATUS.

Application filed February 21, 1924. Serial in). 694,234.

My invention relates to automatic interlocking apparatus, andparticularly to apparatus for automatically controlling traffic overconflicting routes. 4

I will describe one form of interlocking agparatus embodying myinvention, and will then point out the novel features thereof in claims.a

The accompanying drawing is a diagram matic yiew showing one form ofinterlocking apparatus embodying my invention.

Referring to this drawing the reference characters a and 7) designatetivof railway tracks intersecting at a crossing A. The rails 1 and 1 oftrackc are divided by means of insulated joints ,2 into track sectionsD-E, E-F track here similarly divided into sections HJ, JK and KL.within the limits of section EF of track a. and is within the limits ofsection J K of track 6. The crossing A is insulated from the rest of thetracks by insulated joints 2% and the rails of sections EF and J K aremade electrically continuous past the cross' ing by jumper wires 2 inthe usual manner. Adjacent the track section DE is a station Z. Apassing siding 1V is connected with section D-E of traclra by means of aswitch 136. v v

Each track section of each track a and Z) is provided with a trackcircuit comprising a track relay desi nated by the reference character Rwith a suitable distinguishing exponent connected across the railsadjacent one end of the section. and source of energy such as a trackbattery 3 connected across the rails adjacent theother end of eachtracl;

section.

Eastbound over track a is controlled each capable of displaying 2.proceed or a stop indication. Associated with each sig- ,.l S is acircuit controller designated by he reference character X with anexponent corresponding to the location; Each circuit and ll-G, and therails 1 and Pot The crossing is S located at;

y be of any suitable form and are I here shown as semaphore. signals"controller X is arranged to be closed only when the associated signalindicatesstop.

Each circuit controller X controls a signal repeating relay here d.signated by the reference character P with an appropriateexponent. Forexamplerelay P is energized only when signal S is at stop, the circuitfor this relay passing from terminal B of a suitable source of energynot shown in the drawing, througlicircuit controller X wire 6, windingof relay P and backto terminal C, of the same source. Each of theremaining relays P is controlled by the associated signal in a mannersimilarto the control' of relay P by signal S Associated also with eachsignal is a stick relay here designated by the reference character Qwith an" appropriate exponent. 'Ref erring particularly to stick relay Qthe pick up circuit for this relay passes from terminal B, through backcontact 7 oftrack relay R, wire 8. back contact 9 of signal repeatingrelay P wires,10 and 11, and winding of relay back to terminal C. Thiscircuit is closed only when relays P and R are (lo-energized; Relay Q isalso providedwith a stick circuit over wh ch cur rent flows'fromterminal B, through back Contact 12 of track relay R wire 13, frontcontact 14. of relay Q wires 15 and 11, and winding of relay Q back toterminal C. A branch is provided for this sticl: circuit by means ofwhich wire 13 may be connected to terminal B. through back contact 16 ofrelay R It follows that when relay OP is once orR? is de-energized. Thecontrol of each of the remaining stick relays Q is similar to thecontrol of relay Q and will be plain from the drawing.

The "reference-characters T and T designate slow acting or time elementrelays here shown as thermo-sensitiye relays; each comprising a heatingelement 1', and an element 5 of thermo-sensitiv-e materialinsulated'e'lect'rically from the" associated li'eating element {1 butsubj ected to the variations in; the, temperature of this element; Eachofthe thermo sensitive elements 5 is of some material which hasth'echaracteristie of 'de cl'e ising'its electricalresistance responseto increases in the temperature of th s elemen Therm-s er e relay sleet:

trolled over a circuit which may be traced from terminal B, through backcontact 17 of track relay B, wire 13, back contact 19 of stick relay Qwire 20, heater 4 of thermo-sensitive relay T, and back to term1- nal CThe-rmo-sensitive relay T controls an auxiliary relay U over a circuitwhich passes from terminal B, through back contact 17 of track relay B,wire 13, back contact 19 of stick relay Q wires 20 and 21,tl'iermo-sensitive element 5 of relay T, wire 22, winding of auxiliaryrelay U and back to terminal C. The parts are so proportioned that whenheating element 4 of relay T is rte-energized, the resistance ofthermosensitive element 5 of relay T is so great that the current thenflowing through relay U is not of sutlicient magnitude to energize thelatter relay. When the circuit is closed, however, for heating element4, the resulting increase in the temperature of thermo sensitive element5 so decreases the resistance of this element that the current thenflowing through relay U energizes this re lay. Relay T is so constructedthat a con siderable interval of time elapses after the circuit isclosed for the heating element 4 before the resistance ofthermo-sensitive element 5 is sufficiently decreased to allow relay U tobecome energized. It follows that if relay CF is (lo-energized and relayR be comes de-energized the circuit is immediate-- ly closed for heatingelement 4 of relay T but a considerable interval of time 'elapses beforerelay U becomes energized. exact length of this time may be regulated tosuitlocal conditions. Thermo-sensitive relay T is similar to relay T andhas a similar time element, The heating circuit for relay T passes fromterminal B, through back contact 23 of track relay, 11*, wire 24, frontcontact 25 of relay U, wire 23. heat ing element- 4 of relay T and backto terminal C. Wire 24 may also be connected with terminal B over backcontact 23 of relay or back contact 29 of relay B. and it follows thatwhen relay U is energized the heating element of relay T will besupplied with current if one or more of relays R", R and R arede-energized At the expiration of the time interval required forthermo-sensitive element 5 of relay T to sutiiciently reduce itsresistance, current flows from terminal B. through thermo-sensitiveelement 5 of relay T, wire winding of a second auxiliary relay U, andback to terminal C. It is therefore plain that when a circuit is closedfor relay T an interval of time elapses before relay U' is energized.

A directional relay V is provided with one pick up circuit which passesfrom ter-' minal B, through front contact 30 oftrack relay B, wires 31and 32, front contact 33 of relay R wires 34, 34 and 35, winding ofrelay V and. back to terminal C. A sec- The 0nd pick up circuit isprovided for relay V over which current flows from terminal through backcontact 36 of track relay B wires 37, 31, 38 and 39, front contact 40 ofstick relay Q wires 41, 34' and 35, wind ing of relay V and back toterminal C. Current is at times supplied to relay V from a third pick upcircuit which may be traced from terminal B through front contact 42 ofstick relay Q wires 43, 39, 33, 31 and 44 back contact 45 of track relayR, wires 46, 34, 34 and 35, winding of relay V and back to terminal C.Still another or fourth pick up circuit is provided for relay V overwhich current flows from terminal B, through front contact 137 of relayU, wires 38, 31 and 32, front contact 33 of relay B wires 34, 34 and 35,winding of relay V and back to terminal C.

A fifth pick up circuit for relay V peso; from terminal B, through backcontact 36 of relay R wires 37, 31 and 44, back contact 45 of relay R,wires 46 34, 4 and winding of relay V, and back to terminal 0. The sixthpick up circuit for this relay may be traced from terminal B, throughfront contact 30 of relay R, wires 31, 38 and 39, front contact 40 ofrelay Q wires 41, 34 and 35, winding of relay V, and backto terminal C.A seventh pick up circuit is closed when relays R and Q are bothenergized under which conditions current flows from terminal B, throughfront contact 42 of relay Q wires 43, 39, 38,31 and '32, front contact33 of relay R wires 34, 34 and 35,, winding of relay V, and back toterminal Ci Relay V is also provided with a stick circuit over whichcurrent flows from terminal B, through back contact 47 of repeating relay P wires 48 and 50, front contact 51 of relay V, wires 52 and 35,winding of relay V and back to terminal C. Wire mayalso be connectedwith terminal B by back contact of signal repeating relay P it followsthat relay V, havingbeen once encrgized, is maintained in its energizedcondition as long as either relay P" or P is deenergized. The functionand operation of relay V will appear as the "description proceeds.

Each of stop, but each is provided with an oper i circuit which. whenclosed causes the sociated signal to display a proceed ind The circuitfor signal passes from t minal B, throi 'h front contact ,j relay B wirefront .s; relay B wire 56, front contact relay B wire 53, back Contactrelay B wire 60, front contact 61 of signal repeating relay P wire 62,front co tact 63 of signal repeating relay front contact 65 of signalrepeating relay P wire 66, back contact 6. of stick relay Q], wire 68,front contact 69 of relay V, wire i of track 70, operating mechanism ofsignal S and back to. terminal. G. The circuit for: signal S passesfrom. terminal B through front contact 'Zl of. track relay R wire 72',back contact '7 3 of relay R wire 74, front contact 75 of track relay Rwire 76, front contact 7'2 of relay R wire 78., front contact 79'ofrelay P wire 80, front contact 81 of relay P wire 82, front contact 83of relay P wire 84, back contact 85 of relay Q wire 86, front contact 87of relayV, wire 88,v operating mechanism of signal, S and back toterminal C. It should-be particularly pointed out that the operatingcircuits for th signals S and S are carried over front contacts ofdirectional relay V. The circuit for signal S may be traced fromterminal B, through front contact 89 of track relay R, wire 90, frontcontact 91 of track relay R wire 92-, back'contact 93 of track relay Rwire 94, frontcontact 95 of track relay R wire 96, front contact 97 ofrelay P wire 98, front contact 99 of relay P wire 100, front contact101' of relay P wire 102,vback contact 108 of stick relay QP, wire ioperating mechanism of signal S and back to terminal C. The circuit forsignal S may be traced from terminal B through back contact 105 of relayR", wire 106, front contact 107 of'relay R wire 108; front contact 109of relay R ',.wir.es 110 and 111, front contact 112 of relay B wire 113,front contact 114 of relay R wires 115 and 116,,f-ront contact 117 ofrelay R", wire 118,

front contact 119 of relay P wire 120, front contact 121- ofrelay P wire122, front con tact 123 of relay P wire 124, back contact 125 of relay Qwire 126, operating meche anisin of signal S and back to terminal O. Thecircuit just traced is provided with a branch which passes from wire110, through wire 12?, back contact 128 of relay U, and

wire 129 back towire 116. It is therefore clear that when relay U is(is-energized, re: lays 1 3 and R are removedfrom the control ofsignal SAs shown in the drawing ail parts of the apparatus are in the positionscorrespond ing to the normal or unoccupied condition of the track. Underthese conditions all track relays R are energized and all signals Sindicate stop. As a result all signal repeater relays P are energized.and all stick relays Qare ole-energized. Thermo-sensitive relays T and Tare both tie-energized, as areauxiliary relays U and'U Directional relayV is, however energized over front contacts and 33' of track relays Rand R respectively.

In explaining the operation of the apparatus I will first assume-that anorthbound train moves over track 6. As the train enters section H'J,track relay 3* becomes e-energiz th s mpl ing, t a k tact 7 3 thereon;the operating'cirouit for sig ratus.

nail. S which signal thereupon displays a proceed indication. As soon assignal moves away from the stop position circuit controller X opens,thus allowing relay P to become tie-energized. This closes, at backcontact 130 of relay P the pick up circuit forrelay QF. At the sametime, the closing of back contact 17 of relay 1- C0211- pletes' a stickcircuit for relay V. As the train enters' 'section JK, track relay R isdeenergized and the circuit for signal S is then opened at frontcontact75 ofrelay R Signal S therefore goes to the stop position and returnsrelay P to its ener 'iz'ed condition. Prior tothis movement of signal. Showever, the closing of back contact 131 of relay B completes a stickcircuit for stick relay Q and this relay is now maintained in its,energized condition over its own front contact, although its pick upcircuit is open atback contact 130 of relay P3 which is now energized.hen the train moves out of section HIJ, relay R becomes energized butthis does not affect the appa- As the train enters section lG-L, relay Ris ole-energized but signal S does not clear because the operatingcircuit of this signal is open at back contact 67 of stick relay Q NVhenthe train leaves section JK track relay R 'becomes energizedbut stickrelay Q is not tie-energized, the stick circuit for this relay now beingclosed at back contact 132 of track relay R. hen the trainle'avessection K- L, the energizetion of" relay R causes the de-energization ofrelay Qlwhich returns the appa'ratusto its normalicondition. I Theoperation of the apparatus as a southbound traintraverses track 6' issimilar to the operation of the apparatus when a northbound train movesover this track and will 'be readily understood from the foregoing.

1 I will next assume that an eastbound train moves over track a. As thistrain enters section D' E',.the de energization of re lay' R" completesthe operating circuit for signal S whichzthereupon indicates proceed.

'At the same time the opening'of front contact 30 of relay R opens thecircuit for relay V which then becomes (ls-energized. Upon the clearingof signal S after the train enterssectio1r DE, relay Q becomesenergized: and this relay is held its energized' condition until thetrain leaves section" FG as will be clear from the drawing, When thetrain moves outof section the 'energization of relay R com: pletesztliesigrth pick up circuit for relay V which therefore: becomes energized.As the train moves into section F.G, a circuit is closed forrelay V overfront contact 40 of relayQ 'anrl back contact36of track relay B aWhent'he trainjlnoves outof section tli'cn g ationof l' lay completesthe original circuit for relay V and relay Q becomes de-energized, thusreturningthe apparatus to the normal condition.

The operation of the apparatus as a westbound train moves over track awill be understood without further explanation.

I will now assume that a train moving north on track Z) has enteredsection H-J. The, clearing of signal S de-energizes relay P as explainedhereinbefore. If, now, a westbound train on track aapproaches crossingA, the de-energization of relay R as this latter train enters section E-Gr will not clear signal S since the operating circuit for this signalis open at front contact 99 of repeater relay l? which is now open.Signal S therefore remains at stop thus preventing the train on track afrom proceeding past point F. As the train on track I) proceeds pastsignal S this signal goes to stop, thus re-energizing relay P but thecircuit for signal S is now open at front contact 95 of track relay Rde-energized by the entrance of the northbound train into section J-K.When the northbound train clears section JK, the energization of relay Rcompletes the circuit for signal S and the train on track a is thenallowed to proceed over the crossing. Similair protection is afforded toeastbound trains on track a when a northbound train is between points Hand K and, also, trains in either direction over track a are preventedfrom proceeding over the crossing when a southbound train on track Z) isbetween points L and J.

In similar manner, if a train on track a is moving westward betweenpoints G and E or is moving eastward between points D and F, trains ontrack 6 are prevented from negotiating the crossing A.

It should be pointed out that if two trains one on track a and one ontrack Z) should approach the crossing and enter the approach sectionssuch. as sections, L-K and FG at approximately the same time, thede-energization of relay R by the train on track a would de-energizerelay V, thus preventing signal S from clearing till the train on tracka had passed point E. It will thus beseen that trains on track a havesuperiority, that is, if a train on track Z) and a train on track aapproach crossing A at approximately the same time, the train on trackZ) will be held by the corresponding signal till the train on track ahas cleared the crossing. If the train on track I) has however, causedrelay P to be de-energized before the train on track a has enteredsection FG, relay V will be maintained in its energized condition by astick circuit over back contact of relay P Signal S then will display aproceed indication and signal S will be held in the stop position.

It is clear from the drawing, that since the operating circuit for eachsignal is controlled by all the track relays for the correspondingtrack, the signal for any train approaching the crossing will be held atstop if an opposing train on the same track is approaching the crossingfrom the other direction.

If however, an eastbound train occupies section DE, a westbound trainoccupies section FG', and section EF is unoc-.

cupied, a train approaching the crossing on track 5 will be permitted tonegotiate the crossing, since the simultaneous de-energization of relaysP, and R by the trains occupying track a closes the fifth circuit forrelay V thus permitting the operating circuit for signal S or S to beclosed when the back contact of relay 3 or R is closed by a trainapproaching the crossing.

It is desirable to at times permit traflic moves on track 5 through thecrossing A when a train occupies section DE. For example, a train mightbe standing at the station Z, or using the siding W without endangeringtrains on track Z). With my in vention, the interlocking isautomatically released for moves over track b after a train has occupiedsection D E for a given time interval. I will assume a train to bestanding at station Z or using siding W, or in some other way causingthe de-energization of relay B. As soon as such relay becomestic-energized, the closing of its back contact 17 causes the heatingelement Q of thermosensitive relay T to be energized. After aconsiderable time interval the resistance of thermo-sensitive element 5of relay T is so reduced as to allow current to flow there through toenergize relay U. The opening of back contact 128 of relay U opens thebranch around the front contacts of relays R and R in the controlcircuit for signal S If new a train enters section H-J, thede-energization of relay R causes signal S to go to stop. At the sametime a circuit is completed at baclrcontact 23 of relay R and frontcontact 25 of relay U for the heating element of thermo-sensitive relayT After a second considerable interval of time the resistance ofthermo-sensitive element 5 of relay T is so'reduced that relay Ubeconie's energized. The closing of front contact 137 on this relaycompletes the fourth pick up circuit for relay V thus closing thecircuit for signal S". The operation of the apparatus as this trainproceeds through-the track I) or for a southbound train over track 7)will be readily understood without further explanation.

Since thermo-sensitive relay T requires a considerable interval of timefor its operation, a train moving from left to right on track a willordinarily enter section EF before relay U becomes energized. This timeinterval required for the operation of relayT and tliesiinilar timeinterval required for relay T prevent conflicting trains fromsimultaneously approaching the crossing A, but permit trains to moveover track Z) in either direction when a train stands in section DE. u

Although I have herein shown and do scribed only one form of automaticinterlocking apparatns embodying my invention, it is understood thatvarious changes and modifications may be made therein within the scopeof the appended claims without departing from the spirit and scope of myinvention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track, a second trackintersecting said first track, means so controlled "as, to preventtrains on said second track from proceeding past said intersection whena train is occupying said stretch, and means effective at "theexpiration of a time interval f llo ing the entrance of a train intosaid stretch to modify the control of said first means.

2. In combination, a stretch "of railway track, a second trackintersecting said first track, means effective when a 'tra'inoccupiessaid stretch for preventing trailic movements past the crossing oversaid second track, and means 'efiec't'ive at the expiration "of a fixedtime interval following the entrance of a train into said section for attimes allowing traffic through the crossing over said second track.

over said intersection on the second track when a train occupies saidstretch, and means effective atthe expiration of a time intervalfollowing the entrance ofa train into said section for allowing suchmovements of traliic "over said second track.

4, In combination, two interse'ctingrai'lway tracks, means for eachtrack for preventing trains from approaching the intersection over suchtrack when a train on the other track is on or near the intersection,and means for permitting movements over one track when a train isstanding still on the otherv traclr adjacent the intersection.

'5. In combination, two intersecting railway tracks, means foreachtrackfor preventing trains from approaching the intersection oversuch track when a train on the other track'is on or near theintersection, and means including a;thermo-sensitive 'relay for at timespermitting movement-s over one track when a train is standing "still onthe other track adjacent the intersection.

-6. In Combination, two intersectingrailway tr clrs, a signal forgoverningtra' c approaching the intersection over one track and arrangedto indicate proceed when a train approaches said -si'gn al, means forpreventing said 5 nai from indicating-proceed it a train is approachingsaid intersection over said second track, and means for allowing saidsignal to indicate proceed it a train is standing still on said secondtrack adjacent the intersection.

7. In "combination, two intersecting railway tracks, a signal forgoverning traffic approaching the intersection over one track andarranged to indicate proceed when a train approaches said signal, meansfor preventing said signa-l from indicating proceed if a train isapproaching said intersection over said second track, 'andmeansincluding a time element relay for allo'w i said Sig mil to indicateproceed if a train is standing still on said second track adjacent theintersection. I

8. In combination, two intersecting .-rai lway tracks, "acontactarranged to be opera-ted when a train approaches the intersection overone track, trailic governing apparatus for the second track controlledby said contact,

andmea'ns set into operation when said contact is operated "andeifective at the ex-pication of a time interval to remove sai'd conatedwhen a train approaches the intersection over one track, trafficgoverning apparatus for the second track controllechby said contact, andmeans' including atiine element relay for at times removing said.contact from the control "of said tra'fiic Igoverning means.

10. In combination, two intersecting railway tracks, a contact arrangedto be operated when a train approaches tlre intersection over onet'racln trafiic governingapparatus for the second track controlled bysaid contact, and means incli' ding a time element relay set intooperationw'hen said cont-act is operated and elfective at the expiration"of a time interval to remove said contact from the control of saidtr'aific governing means.

11. In combination, two intersecting railway traclzs, a contact arrangedto be operated when a train approaches the intersection over.on'e'track, trafiic governing apparatus for the second trackcontrol'l'ecl'by said cen'taet,means set into operation when saidcontact is operated and eiie'cjt'rve at the expiration of a timeinterval to remove said contact from the control of said manic.governing means, andmeans; for operating said 'trafiic means when trainon said second track approaches the intersection. V v v I 12. In'eonijb'in "ti'on, two intersectin railway tracks, cont'act arranged tobe op'erated when a train approaches the intersection over one track,traffic governing apparatus for the second track controlled by saidcontact, means including a time element relay for at times removing saidcontact from the control of said trafiic governing means, and means foroperating said traflic governing means when a train on said second trackapproaches the intersection.

13. In combination, two intersecting rail way tracks, a contact arrangedto be operated when a train approaches the intersection over one track,trafiic governing apparatus for the second track controlled by saidcontact, means for at times removing said contact from the control ofsaid tra'tlic governing means, and means arranged to be set intooperation by a train approaching the crossing on the second track whensaid contact is removed from the control of the traliic governing meansand etiective atthe expiration of a time interval to operate saidtrafiic governing means. I

14. In combination, two intersecting railway tracks, a relay arranged tobe de-energized when a train approaches the intersection over one track,means set into operation when said relay is tic-energized and effectiveat the expiration of a time interval for again energizing said relay,and trailic governing means for the second track controlled by saidrelay.

15. In combination, two intersecting railway tracks, a relay arranged tobe dc-energized when a train approaches the lntersection over one track,means set into operation when said relay is de-energized and eiiectiveat the expiration of a time interval for again energizing said relay,and means tor preventing traffic from passing over said intersection onthe second track when said relay is tie-energized.

16. In combination, two intersecting railway tracks, a relay arranged tobe de-energized when a train approaches the intersection over one track,means for again energizing said relay at the expiration ofa timeinterval, and trafiic governing means for the second track controlled bysaid relay.

17. In combination, two intersecting railway tracks, a relay arranged tobe de-energized when a train approaches the intersection over one track,means including a time element relay for again energizing said relay atthe expiration of a time interval, and traffic governing means for thesecond track controlled by said relay.

18. In combination, two intersecting railway tracks, arelay arranged tobe de-energized when a train approaches the intersection over one track,means set into operation when a train approaches the intersection overthe second track and effective at the expiration of a time interval foragain energizing said relay, and traiiic governing means for the secondtrack controlled by said relay.

19. In combination, two intersecting railway tracks, a track relay forone track arranged to be de-energized when a train approaches theintersection over such track, an auxiliary relay arranged to beenergized at the expiration of a time interval following de-energizationof said track relay, and trafiic governing means for the second trackcontrolled by said auxiliary relay.

20. In combination, two intersecting railway tracks, a track relay forone track arranged to be ole-energized when a train approaches theintersection over such track, a slow acting relay controlled by saidtrack relay, and trafiic governing means for the second track controlledby said slow acting relay.

21. In combination, two intersecting railway tracks, a track relay forone track arranged to be de-ener ized when a train approaches theintersection over such track, a slow acting relay controlled by saidtrack relay, an auxiliary relay controlled by said slow acting relay,and traffic governing means for the second track controlled by saidauxiliary relay.

22. In combination, two intersecting railway tracks, a track relay forone track arranged to be de-energized when a train approaches theintersection over such track, a slow acting relay controlled by saidtrack relay, a second track relay for said second track arranged to bede-energized when a train approaches the intersection over such secondtrack, an auxiliary relay controlled by said relay and by said secondtrack relay, and trafiic governing means for said second trackcontrolled by said auxiliary relay.

23. In combination, two intersecting railway tracks, a track relay forone track arranged to be de-energized when a train approaches theintersection over such track, a time element relay controlled by saidtrack relay, and traiiic governing means for each said track controlledby said time element relay. 7

24. In combination, two intersecting railway tracks, a track relay forone track arranged to be de-energized when a train approaches theintersection over such track, a slow acting relay controlled by saidtrack relay, traflie governing means for the first said track controlledby said slow acting relay, a second slow acting relay controlled by thefirst said slow acting relay, and traffie governing means for the secondtrack controlled by said second slow acting relay.

25. In combination, two intersecting railway tracks, a track relay forone track arranged to be de-energized when a train approaches theintersection over such track, a thermo-sensit-ive relay controlled bysaid track relay, an auxiliary relay arranged to ill) be energized atthe expiration of a time interval following the energization of saidthermo-sensitive relay, a second track relay for said second track andarranged to be deenergized when a train approaches said crossing oversuch second track, traflic governing means for said first trackcontrolled by said second track relay and by said auxiliary relay, asecond thermo-sensitive relay controlled by said auxiliary relay, asecond auxiliary relay controlled by said second thermosensitive relay,a directional relay controlled by said first track relay and by saidsecond auxiliary relay, and traffic governing means for said secondtrack controlled by said directional relay.

26. In combination, two intersecting railway tracks, a stick relayarranged to be energized when a train approaches the intersection movingin one direction along the first track, a track relay arranged to bedeenergized as such train recedes from the intersection, a directionalrelay controlled by said sticlr relay and by said track relay, andtratlic governing means for the second track controlled by saiddirectional relay.

2?. In combination, two intersecting railway tracks, a stick relayarranged to be energized when a train approaches the intersection movingin one direction along the first track, a track relay arranged to be de'ized as such train recedes from the invLion, a directional relaycontrolled by said sticlr relay and by said track relay, traiiicgoverning means for the second track controlled by said directionalrelay, and means operated by said tratlic governing means for modifyingthe control of said directional relay.

28. In combination, two intersecting railway tracks, a stick relayarranged to be energized when a train approaches the interer 'ion movingin one direction along the track, a. track relay arranged to be desed assuch train recedes from the inersection, an auxiliary relay controlledby said track relay; directional relay controlled by said auxiliaryrelay, said stick relay and said track relay; and trafic governing meansfor the second track controlled by saiddirectional relay.

29. In combination, two intersecting railway tracks, a stick relayarranged to be energized when a train approaches the intersection movingin one direction along the first track, a track relay arranged to bedecnergized as such train recedes from the intersection, a second trackrelay arranged to be (ls-energized when a train moving in the oppositedirection over said first track'approaches the crossing, slow actingmeans controlled by said second track relay, an auxiliary relaycontrolled by such slow acting means; a directional relay controlled bysaid stick relay, said first track relay and said auxiliary relay; andtratfic governing means for the second track controlled by saiddirectional relay.

30. In combination, two intersecting railway tracks, signals for saidtracks intercontrolled to prevent two trains on said two tracirsrespectively from meeting at the intersection, and slow acting means setinto operation when a train on one track approaches said intersectionfor releasing the signals for the other track after a given interval or"time.

31. In combination, two intersecting railway tracks, signals for saidtracks intercontrolled to prevent two trains on said two tracksrespectively from meeting at the intersection, an electrically isolatedsection in one of said tracks on one side of said intersection, and slowacting means set into op eration when a train approaching saidintersection enters said section for releasing the signals for the othertrack it such train remains in said section for more than a giveninterval of time.

32. In combination, two intersecting railway tracks, signals for saictracks intercontrolled to prevent two trains on said two tracksrespectively from meeting at the intersection, and slow acting means setinto operation when a train approaching Said intersection on one trackente s a given portionoi such track for releasing the signals for theother track it the train consumes more than a given amount of time inpassing through said portion of track.

In testimony whereof I aiiix my signature.

LESTER E. SPRAY.

lUU

